Piston expander



Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE 14 Claims.

This invention relates to expanding means for skirts of pistons adapted for use in engines, such as internal combustion engines, compression engines, steam engines and the like.

It is usual to provide such pistons with a head and a skirt which is partially or wholly separated from the head by a circumferential opening or openings. The lands between the ring grooves on the head are usually made slightly smaller in diameter than the diameter of the skirt which is formed initially to closely fit the interior of the cylinder. The skirt, particularly when formed of aluminum or similar metal, is usually slotted longitudinally to permit the skirt to expand and contract so that it will closely follow the cylinder wall. However, due to wear of the cylinder and the piston this closeness of fit between the skirt and the cylinder wall is soon destroyed with the attendant results of piston slap, undue leakage of the oilpast the piston rings, and decreased efliciency of the engine. In order to overcome these defects without reboring the cylinders or replacing the pistons, it has been heretofore suggested that spring means of some sort within the skirt be provided to expand the skirt.

The principal object of my invention is to provide an improved and simple expander which exerts an expansive action substantially about the entire skirt while permitting the skirt to contract when necessary in operation, and thereby attain a more perfect fit between the worn skirt of downwardly extending fingers which may form in efiect a split wall adapted to engage and bear against the inner surface of the piston skirt over a substantial area to force it radially outward to conform to a worn or out-of-round cylinder. For this purpose, a pair of oppositely disposed expanding fingers or wall sections bear against the slotted portion of the skirt and that portion opposite thereto, while another pair of fingers or wall sections may engage and press outwardly against the opposed boss portions, to expand the circumferential length of the skirt. 7

The full nature of the invention will be more clearly understood from the accompanying drawing and the following description and claims:

Figrl is a central vertical section through a mally exert an outward pressure thereon.

piston with the expander mounted therein. Fig. '2 is a section taken on the line 2-2 of Fig. 1. Fig. 3 is a plan view of the under side of the piston showing the expander therein. Fig. 4 is a perspective' view of the expander removed from the piston. Fig. 5 is the same as Fig. 4 showing a modified form of the expander. Fig. 6 is the same as Fig. 4, showing a second modified form. In the drawing there is shown a piston of the usual type having a head I0, piston ring grooves II, a peripheral slot l2 partially separating the head from the skirt l3, and inwardly extending projections in the form-of piston pin bosses l4.

Said skirt is provided with a substantially longitudinal slot extending from the lower end to the peripheral slot I2 on one side thereof intermediate the bosses, to permit of expansion and contraction to conform to the cylinder in which it. operates. I For yieldingly expanding said skirt and imparting thereto a radial outward force under spring tension, there is provided an expander spring as illustrated in Fig. 4. Said spring is substantially I U-shaped or cup-like, being adapted to be forced in inverted position upwardly within the piston skirt toward the head so that the downwardly extending expanding fingers or split wallt sections bear against the inner surfaceor side walls of the split skirt of the piston.

To permit of the flexing of the expander under pressure, it may be described as having a bight portion l6 adapted to lie adjacent the piston'head. Extending downwardly from said bight portion, there are a pair of wall sections or resilient fingers l1 curved to conform with the curvature of the piston skirt and adapted to be forced inwardly against the inherent spring tension therein when mounted within the skirt so as to nor- Intermediate said fingers I1, there are oppositely disposed wall sections or cars 18, which are so head H6 is provided with wall sections ill to engage that portion of the skirt intermediate the bosses while sections I I8, provided with apertures H9, embrace and extend below the boss portions so as to bear thereagainst. I v

While the expander is herein shown specifically as embodying oppositely disposed fingers and intermediate oppositely disposed ears, it may embody suitable expansion folds 220 separating the corresponding wall sections thereof as illustrated in the modified form shown in Fig. 6.

From the foregoing, it will be observed that wherein a piston having a split skirt is caused to operate in an enlarged cylinder or an out-ofround cylinder, or wherein said piston has lost its normal inherent expanding force, the installation of said expander therein will cause the skirt to spread so as to accommodate it to the cylinder in which it operates, while permitting of contraction owing to the longitudinal slot therein and the yielding character of the expander.

It will also be noted that by reason of the cup shaped formation of the expander, it may be readily inserted in the piston and driven home therein without the requirement of unusual tools.

The invention claimed is:

1. In combination with a piston having piston pin boss portions, and a skirt having a substantially longitudinal slot, of a compressible expander sprung into position within said skirt, the said expander being substantially U-shaped with the bight portion thereof lying adjacent the head of the piston and the freely extending finger portions bearing against the inner surface of the skirt under spring tension so as to normally exert an outward pressure thereon, and oppositely disposed intermediate ears extending from the bight portion of said expander in engagement with said boss portions for exerting an outward pressure thereagainst.

2. In combination with a piston having a head, piston pin boss portions, and a skirt having a substantially longitudinal slot intermediate said boss portions, of a compressible cup-like expander sprung into position within said skirt in inverted position with the bight portion thereof lying adjacent the head of the piston, oppositelydisposed depending wall portions of curved cross section conforming substantially to the curvature of the piston skirt extending downwardly from the bight portion into engagement with the portions of the skirt intermediate the boss portions, one of said depending wall portions bearing against said skirt on each side of said slot, and intermediate wall portions extending downwardly from the bight portion into engagement with the boss portions for locking the expander in place and exerting an outward pressure against the boss portions of the skirt.

3. The combination with a piston having a head, piston pin boss portions, and a skirt having a substantially longitudinal slot intermediate said boss portions, of a compressible cup-like expander sprung within said skirt in inverted position with the bight portion thereof lying adjacent the head of the piston, oppositely-disposed depending wall portions extending downwardly from the bight portion into sliding frictional engagement with the skirt intermediate the boss portions, one of said depending wall portions bearing against said skirt on each side of said slot, and intermediate members extending downwardly from the bight portion over said boss portions for preventing escape of the expander from the piston when in operation.

4. The combination with a piston having a split skirt and oppositely disposed crank pin bosses, of a spring piston expander located within the piston skirt and presenting line contacts with the skirt to each side of the split and in substantial parallelism therewith, and likewise bearing directly against each boss above its center line only and at that side thereof nearest the split.

5. The combination of a piston having a head, a slotted piston skirt, and piston pin bosses; and a piston skirt expander, said expander comprising oppositely disposed spring arms, said arms extending at an angle to the axis of said piston and converging toward said piston head, and means intermediate the upper portions of said spring arms encircling said piston pin bosses.

6. An expander for pistons comprising a U- shaped plate member formed from a steel stamping the sides of which comprise spring arms, and a perforated lobe projecting from said U-shaped member between said arms, said lobe lying in a plane parallel to a medial plane intersecting said arms.

7. An expander for pistons comprising a U- shaped plate member the sides of which comprise spring arms, and a pair of spaced perforated lobes projecting from said U-shaped member between said arms, said lobes being disposed in opposition and lying in planes parallel to a medial plane intersecting said arms.

8. An expander for pistons comprising a spring steel stamping having oppositely disposed platelike wings having spaced ends adapted to form spring arms and oppositely disposed lobes intermediate the wings and the common axis of said lobes being at right angles thereto.

9. An expander for pistons comprising a U- shaped plate member the sides of which comprise spring arms, the free ends of said arms being arcuate in a transverse plane, and a pair of spaced perforated lobes projecting from said U-shaped member between said arms, said lobes being disposed in opposition and lying in planes parallel to a medial plane intersecting said arms.

10. An expander for pistons comprising oppositely disposed plate-like wings adapted to form spring arms having spaced ends and oppositely disposed lobes intermediate the wings and connecting necks between the lobes and the wings.

11. A piston skirt expander comprising a resilient body constructed to be positioned in a piston crosswise of a piston pin, said body having end portions arranged for engagement with opposite sides of a piston skirt at points intermediate the usual pin bosses, and lobes carried by and extending from said resilient body, said lobes being perforated to permit the passage of a piston pin therethrough.

12. A piston skirt expander comprising a resilient element having arcuate skirt-engaging portions, and a pair of opposed lobes extending from said resilient element intermediate said arcuate skirt-engaging portions, said lobes being perforated to permit the passage of a piston pin therethrough.

13. A piston skirt expander adapted for use with an expansible and contractible piston skirt carrying connecting rod supporting means in cluding bosses, which comprises a spring metal member adapted to extend crosswise of the connecting rod supporting means with its opposite ends adapted to engage against opposite sides of the skirt ,under tension, and resilient sheet metal lobes intermediate the ends of said member and to one side of the longitudinal median line thereof and adapted to have the connecting rod supporting means project therethrough, and the lobes being also adapted to exert outward pressure against said bosses.

14. An expander for pistons comprising a spring metal member having oppositely disposed spring portions which are of substantially arouate shape in a transverse plane and which are adapted to engage the opposed walls of an expansible and contractible piston skirt, and a pair of spaced, perforated lobes projecting from said member intermediate said portions, said lobes being parallel to a median plane intersecting said portions and constructed and arranged for engagement with connecting rod support means for supporting the expander within the piston skirt. 5

WALTER J. SIX. 

